[petsc-users] Regarding help with MatGetSubMatrix parallel use

[Krishnan, Gautham]

Hello,

For a CFD code being developed with FORTRAN and MPI, I am using PETSC matrices and for a particular operation, I require to extract a submatrix(n-1 x n-1) of a matrix created (n x n). However using the petsc MatGetSubMatrix works for serial runs but fails when the domain is split up over PEs- I suspect the indexing changed for parallel runs and hence the global indexing that worked for serial case just shuffles around matrix entries in parallel undesirably. I would like to ask whether anybody could offer some guidance regarding this.  I would like to note that the 2D domain is split along both x and y axes for parallel runs on multiple PEs.

Regards,
Gautham Krishnan,

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